function run() {
    var obj = {}
    obj.a = 1
    obj.b = 2
    obj.c = obj.a + obj.b

    var result = Object.keys(obj)
    for(var i = 0; i < result.length; i++) {
        console.log(result[i])
    }
    console.log(typeof result)

    console.log("check a  in obj:")
    console.log("a" in obj)
}